title: Multiple-input single-output closed-loop isometric force control using asynchronous intrafascicular multi-electrode stimulation.
abstract: Although asynchronous intrafascicular multi-electrode stimulation (IFMS) can evoke fatigue-resistant muscle force, a priori determination of the necessary stimulation parameters for precise force production is not possible. This paper presents a proportionally-modulated, multiple-input single-output (MISO) controller that was designed and experimentally validated for real-time, closed-loop force-feedback control of asynchronous IFMS. Experiments were conducted on anesthetized felines with a Utah Slanted Electrode Array implanted in the sciatic nerve, either acutely or chronically ( n = 1 for each). Isometric forces were evoked in plantar-flexor muscles, and target forces consisted of up to 7 min of step, sinusoidal, and more complex time-varying trajectories. The controller was successful in evoking steps in force with time-to-peak of less than 0.45 s, steady-state ripple of less than 7% of the mean steady-state force, and near-zero steady-state error even in the presence of muscle fatigue, but with transient overshoot of near 20%. The controller was also successful in evoking target sinusoidal and complex time-varying force trajectories with amplitude error of less than 0.5 N and time delay of approximately 300 ms. This MISO control strategy can potentially be used to develop closed-loop asynchronous IFMS controllers for a wide variety of multi-electrode stimulation applications to restore lost motor function.
authors.affiliation: Department of Mechanical Engineering, University of Utah, Salt Lake City, UT 84112, USA. m.frankel@utah.edu
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Frankel
authors.forename: Brett R
authors.initials: BR
authors.lastname: Dowden
authors.forename: V John
authors.initials: VJ
authors.lastname: Mathews
authors.forename: Richard A
authors.initials: RA
authors.lastname: Normann
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Clark
authors.forename: Sanford G
authors.initials: SG
authors.lastname: Meek
mesh_terms: D000465:Algorithms; D000758:Anesthesia; D000818:Animals; D001369:Axons / Q000502:physiology; D002138:Calibration; D002415:Cats; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation / Q000379:methods*; D004567:Electrodes, Implanted; D004867:Equipment Design; D005528:Foot / Q000294:innervation / Q000502:physiology; D005684:Gait / Q000502:physiology; D007537:Isometric Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D012371:Robotics; D012584:Sciatic Nerve / Q000502:physiology; D014584:User-Computer Interface